The present invention relates to an optical member holding device capable of adjusting relative position of a first optical member and a second optical member, and to an optical scanning device provided with the holding device, and an image forming device provided with the scanning device.
A conventional electrophotographic image forming device such as a laser printer and a copier provides an image forming section where a photosensitive body is charged, and the surface of the photosensitive body is exposed to a laser beam irradiated from an optical scanning device to form an electrostatic latent image. The image is then visualized by a developer such as toner and the toner image is transferred onto a recording medium such as paper. A fixing device is provided for heating the toner image and fixing the image to the recording medium. In the optical scanning device, a laser beam is generated from a point source such as a laser diode (hereafter referred to as an “LD”) and is collimated to parallel light by a collimator lens. A slit regulates a spread of the light flux. The light flux is converged by a cylindrical lens to refract only one direction and is focused on a rotating polygon mirror. Reflected on the polygon mirror, the light flux is scanned unidirectionally, passes various lenses and mirrors, and is irradiated to the photosensitive body from the optical scanning device. Such optical scanning device must highly accurately align the start point of the light flux, i.e., the relative position between the LD and the collimator lens must be accurately provided, otherwise the degree of defocus increases on the subsequent optical paths.
Japanese Patent Application Laid-Open Publication No. 2000-284203 discloses a lens holder (lens cell) supporting the collimator lens and an LD holder supporting the LD. The lens holder and the LD holder are fixed to a supporting member (supporting section). The lens holder can be displaced with respect to the supporting member in the optical axis direction of the laser beam for focus adjustment. The LD holder can be displaced in a direction parallel to a face opposite to the supporting member for the purpose of focus adjustment toward a plane direction orthogonal to the optical axis direction of the laser beam. During the position adjustment, the lens holder is temporarily fixed to the supporting member by means of a retaining spring and is then finally fixed with an adhesive. The position of the LD holder is fixed by a screw after the position adjustment of the LD holder.
However, the LD holder and the supporting member contact with each other on their surfaces. The contact surfaces are distortingly fixed to each other due to the fixing with the screw. A distortion occurs between the contact surfaces in the direction of rotation of the screw. This distortion causes misalignment between the LD and the collimator lens, deforming an image to be formed.